The present invention relates to a method for producing magnetic head used in a magnetic recording/reproducing system, more particularly to a magnetic head having mold glass filled into a slot for regulating a track width thereof.
A conventional magnetic head is shown in FIGS. 1A to 1D. In the figure, a magnetic head 1 comprises magnetic core half bodies 2 and 3 made of ferromagnetic materials such as a single crystal ferrite of manganese and zinc, a gap spacer 4 attached to the half bodies 2 or 3, and a binder 5 for uniting the half bodies 2 or 3 one with the other and made of solidified glass to which a mold glass is cooled and hardened.
The half body 2 has a winding guide 2a which is cut off a part of the outer end from the body 2, a winding groove 2b cut out of a part of an inner end wall thereof, and a pair of track width regulation grooves 2c which are cut out of top parts of both side corners of the body 2. The half body 3 has a winding guide 3a cut out of the outer end wall of the body 3, a back groove 3b cut out of the bottom corner of the inner side of the body 3, and a pair of track width regulation grooves 3c which are cut out of top parts of both side corners of the body 3 corresponding to the grooves 2c.
The head 1 has a tape sliding surface 1a formed at the upper surface thereof, and a magnetic gap 1b made by the gap spacer 4. The gap spacer 4 is formed in a thin layer and made of non-magnetic substances such as silicon oxide (SiO.sub.2), aluminum oxide (Al.sub.2 O.sub.3) or the like, which are harder than the glasses and have a high melting point. On the sliding surface 1a, a track width regulation portion is formed by the grooves 2c and 3c for regulating a track width of a magnetic tape (not shown). As the gap spacer 4 lies between the upper portions of the half bodies 2 and 3, the gap spacer 4 causes the bodies 2 and 3 to have an angle of theta degrees. Mold glass pieces 5 are caulked in the back groove 3b and the regulation grooves 2c and 3c, respectively. A gap 6 at an angle of theta degrees is formed between the inside surfaces of the bodies 2 and 3 by the gap spacer 4 the magnetic gap 1 b being extended downward in the figures.
The magnetic head 1 having the above configuration is manufactured by a method including the following steps. At first, two pole-shaped materials respectively corresponding to five or six half bodies 2 and 3 are provided and a spacer material corresponding to five or six gap spacers 4 is located between upper portions of core materials. At this time, two long grooves have been already formed at predetermined portions of the inside and outside surfaces of the material of the body 2 in the longitudinal direction respectively corresponding to the guide 2a and groove 2b. Two long grooves have been already formed at predetermined portions of the inside and outside surfaces of the material of the body 3 in the longitudinal direction respectively corresponding to the guide 3a and back groove 3b, also.
Secondly, glass rods which melt at a predetermined temperature are respectively allotted to positions coresponding to the regulation grooves 2c and 3c. The same glass rod is allotted to a position corresponding to the back groove 3b. Then, the glass rods are melted by adding at a predetermined temperature while the materials continue to have a predetermined angle theta. As the glass is cooled down and solidified after melting, the materials are fixed by the solidified glass material.
Lastly, after an upper surface of the materials connected in a pole-shaped body is polished and shaped in an arc, the materials are cut in five or six pieces having a predetermined width. After that, the magnetic head 1 shown in FIGS. 1A to 1D is completed.
The magnetic head 1, which has the aforementioned configuration and is manufactured by the above method, is formed in the manner of having the magnetic gap 1b, so that the gap 6 must be formed at a lower joint plane of the half bodies 2 and 3. The head 1 has a problem that the gap 6 causes the head 1 to form a crack 7, thereby generating a problem of a large deterioration in the mechanical strength.
In order to prevent the crack occurring in the above example, there is proposed a magnetic head 10 according to another conventional example as shown in FIGS. 2A to 2D. The head 10 comprises half bodies 12 and 13, respectively corresponding to the bodies 2 and 3, and which are joined by a binder 15 corresponding to the binder 5 of the head shown in FIGS. 1A to 1D. Accordingly, the half bodies 12 and 13 have winding guides 12a and 13a and winding grooves 12b and 13b, respectively. Furthermore, both sides along joined end surfaces of the bodies 12 and 13 are cut out to form uniting grooves 12c and 13c in which the binder 15 is plugged. An upper surface of the head 10 is formed into an arc shape to become a tape sliding surface 10a, and a track regulation groove is formed by the binder 15. A magnetic gap 10b is formed by a united plane of the bodies 12 and 13 on the sliding surface 10a in the same manner as the aforementioned example shown in FIGS. 1a to 1D.
As the magnetic head 10 according to the prior art shown in FIGS. 2A to 2D is manufactured by substantially the same steps as those of the head 1 shown in FIGS. 1A to 1D, duplicate explanation is omitted.
In the example, as shown in FIG. 2C which is a cross sectional view of FIG. 2A on a cutting line II--II, though the binder 15 after solidification of the mold glass is provided around the lower united plane of the bodies 12 and 13, the head 10 has a problem that a gap 16 is formed between the bodies 12 and 13. As a joined area of a back gap portion, that is, the lower united area between the bodies 12 and 13 becomes smaller, a magnetic reluctance becomes larger, so that the head 10 has the problem of the magnetic characteristics deteriorating.
The magnetic head 10 is not only used as the complete head having a single magnetic gap 10b shown in FIG. 2D, but also as a so-called double azimuth head comprising two heads which are cut off at cutting lines 17 of the bodies 13, as represented by the dotted line shown in FIG. 2D, respectively, and set on a base (not shown). In the case that the heads 10 are used in the double azimuth head, it is possible to cut off the back grooves 13b when the bodies 13 are cut, because the distance between the cutting line 17 and the back groove 13b is insufficient. Therefore, the head 10 involves the problem of checking the workability of the manufacture of the head.
The former head 1 has a crack 7 or the like and has a smaller joined area of the half bodies, as mentioned before, so that the head has the problem of a deteriorated magnetic resistance and other magnetic characteristics.